When performing a surface wave test, indications may arise from which of the following?

When performing a surface wave test, all listed factors can contribute to the development of indications. Surface discontinuities are the primary focus of the test, as these are the flaws or defects on the material's surface that the test aims to detect. However, extraneous items such as oil and dirt can also interfere with the test results.

Oil on the surface can dampen the ultrasonic waves or change their propagation characteristics, leading to false readings or masking real indications. Similarly, dirt and other contaminants could obstruct the ultrasonic signal, thus affecting the interpretation of the test.

Therefore, the presence of surface discontinuities, oil, and dirt can all result in indications during a surface wave test. This comprehensive view underscores the importance of a clean testing environment and the consideration of all potential factors that might influence the results during the test.